1. Field of the Invention
The invention relates to a derailleur apparatus for bicycles, and more particularly to the derailleur apparatus that is mounted on a handle of the bicycle for providing the rider a convenient gearshift (i.e. derailleur) manipulation while in riding.
2. Description of the Prior Art
Bicycles are good gears for both transportation and environmental protection. Especially for nowadays leisure lifestyle, outdoor activities to experience the nature atmosphere are the most relevant sport and health pastime to people. In particular, the derailleur bicycle is featured in adapting a derailleur apparatus to perform gearshifting so as to allow the rider to switch the maneuvering between a low gear for an uphill operation and a high gear for a downhill. Thereby, merits of saving labor for the uphill operation and saving time for the downhill operation can be easily achieved.
By having a Taiwan patent publication No. 315826 for example, the derailleur operating apparatus for bicycles is disclosed to be mounted on a handle of the bicycle and include at least a supportive member, a reeling member, a clutch mechanism, a releasing assembly, an engaging assembly and a transmission mechanism. The supportive member formed as a step-shaped pipe has a disc and a spindle extended upward from the disc. A bottom of the disc is fixed to the handle of the bicycle. The reeling member pivotally mounted at the spindle of the supportive member is to pull tightly or release a cable. The clutch mechanism including a meshing member is to be fixed by a fixation plate so as to pose the reeling member at a specific angle for being fixed further to the disc of the supportive member. The releasing assembly has a lower driving lever to disengage the clutch mechanism from the reeling member, such that the reeling member can be pivotally mounted at the spindle of the supportive member in a manner of releasing the cable by freely rotating the reeling member. The engaging assembly has an upper driving lever pivotally mounted at the spindle of the supportive member. The transmission mechanism has an actuated member connected fixedly with the upper driving lever for triggering the upper driving lever so as further to drive the transmission mechanism. Thereby, the reeling member is driven to rotate so as to pull tightly the cable. As the reeling member freely rotates to release the cable, the actuated member would stop temporarily the reeling member. Upon such an arrangement, the up-shift and low-shift respectively through the pulling and releasing the cable by the reeling member can be achieved by the co-movement of the lower driving lever, the clutch mechanism, the upper driving lever and the transmission mechanism.
The aforesaid patent disclosure is actually one kind of conventional gearshift manipulation apparatuses for bicycles, which is to perform the up-shift and low-shift respectively through the pulling and releasing the cable by the reeling member. However, in such a design of the conventional gearshift manipulation apparatus for bicycles, the driving lever is usually located at the grip of the bicycle for the rider. Therefore, while a rider shifts the gears, one of his/her hand needs to leave the grip so as able to push the upper or the lower driving lever, particularly along a single direction. Obviously, such a design make cumbersome for maneuvering the bicycle. Importantly, in a racing situation, the gearshift becomes a burden to the rider. For the rider's finger needs to stay at a position close to at the upper and the lower driving lever, stiffness upon this finger would be inevitable after a long term riding. As a consequence, the later-time gearshift operation would be significantly slowed due to the fatigue at the finger, and thus a unexpected loss in a racing due to the deferred gearshifting would be highly possible.
By having a Taiwan patent No. I286978 for another example, the derailleur apparatus for bicycles includes an installation portion on the bicycle, a reeling body, a position sustaining/releasing mechanism, an action member and an input member. The reeling body is located at the installation portion for pulling and releasing the cable. The position sustaining/releasing mechanism is to keep a cable stop selectively held at one of a plurality of gearshift positions. The action member is pivotally mounted the installation portion about a first axis. While the action member swings away from a neutral position so as to reach a gearshift position, the position sustaining/releasing mechanism would allow the reeling body to pull the cable. The input member constructed at the action member is to determine the swinging direction of the action member, either in a first direction or a second direction. upon such an arrangement, the rider can determine a favorite direction to operate the gearshifting.
Though a bi-directional gearshift operation can be provided by the aforesaid disclosure, yet the structuring of the derailleur apparatus is complicated and thus derailing sensitivity would be low due to the inevitable integrated mechanical tolerance. In addition, the production cost and the following maintenance expense would be hard to be reduced.